The fibre channel (“FC”) is an architecture and protocol for a data communication network that interconnects a number of different combinations of computers and peripheral devices. The FC supports a variety of upper-level protocols, including the small computer systems interface (“SCSI”) protocol. A computer or peripheral device is linked to the network through an FC port and copper wires or optical fibers. An FC port includes a transceiver and an interface controller, and the computer peripheral device in which the FC port is contained is called a “host.” The FC port exchanges data with the host via a local data bus, such as a peripheral computer interface (“PCI”) bus. The interface controller conducts lower-level protocol exchanges between the fibre channel and the computer or peripheral device in which the FC port resides.
A popular paradigm for accessing remote data in computer networks is the client/server architecture. According to this architecture, a client computer sends a request to read or write data to a server computer. The server computer processes the request by checking that the client server has authorization and permission to read or write the data, by mapping the requested read or write operation to a particular mass storage device, and by serving as an intermediary in the transfer of data from the client computer to the mass storage device, in case of a write operation, or from the mass storage device to the client, in case of a read operation.
In common, currently-available and previously-available communication network architectures, the server computer communicates with the client computer through a local area network (“LAN”) and the server computer communicates with a number of mass storage devices over a local bus, such as a SCSI bus. In such systems, the server is required to store and forward the data transferred as a result of the read or write operation because the server represents a bridge between two dissimilar communications media. With the advent of the FC, client computers, server computers, and mass storage devices may all be symmetrically interconnected by a single communications medium. The traditional client/server architecture is commonly ported to the FC using the same type of client/server protocols as are used in the LAN and SCSI networks discussed above.
SCSI-bus-compatible mass-storage devices, including high capacity disk drives, are widely available, and widely used, particularly in mid-sized and large-sized computer systems, and many FC-based systems employ FC-compatible disk drives, each including one or more FC ports and logic needed for the disk drives to function as FC responders. In smaller systems, including personal computers (“PCs”), a different family of disk drives, referred to as Integrated Drive Electronics (“IDE”) or Advanced Technology Attachment (“ATA”) disk drives is widely employed. A serial ATA disk (“SATA”) generally interconnects with a system via an Industry Standard Architecture (“ISA”) bus.
The present invention is related to FC, SCSI, and IDE/ATA technologies. Each will be discussed, in turn, in three separate subsections, below. Those familiar with any or all of these technologies may wish to skip ahead to the final subsection of this section, describing FC-based disk arrays, and to the Summary of the Invention section that immediately follows that subsection.